1. Field of the Invention
The present invention relates to systems and methods for target tracking and imaging. More specifically, the present invention relates to synthetic aperture ladar systems.
2. Description of the Related Art
The resolution of a typical conventional radar system is dependent on the antenna size. Accordingly, unless the antenna diameter is quite large, the resolution is low. Synthetic aperture radar (SAR) provides a larger effective antenna size by virtue of the movement of the aperture relative to the target and integration of the returns from the target.
However, current and future applications will require further improvements in resolution, particularly angular resolution, to achieve longer range and improved imagery. This need is addressed somewhat by synthetic aperture ladar (SAL). SAL systems are similar to radar systems with the exception that a laser pulse is transmitted as opposed to a radio wave. However, SAL systems tend to be too complex and costly for many current and future applications.
Further, current synthetic aperture ladar approaches are based largely on existing synthetic aperture radar systems operating in the millimeter wave regime. These approaches use coherent heterodyne processing to extract precise Doppler information from the target signal, which is then synthesized into a high resolution angle-angle-range image using SAR image formation algorithms. Phase errors resulting from nonlinear flight trajectories are compensated using SAR auto-focus algorithms that work quite well in the millimeter regime, but may be difficult to implement at optical wavelengths, where the required sensitivity is increased several orders of magnitude.
Accordingly, a need exists in the art for a more simple and less costly system or method for providing improved resolution in a target tracking and optical imaging application. Furthermore, there is a need for an alternative for those applications that do not require three-dimensional imagery for which high-resolution angle-angle images will suffice.